Overhead service units in which a platform is carried upon a series of slidably interconnected frames for raising and lowering the platform have long been known in the art. One such unit is shown in U.S. Pat. No. 3,031,027.
It has been a common practice in such units to employ a single hydraulic cylinder and to interconnect the frames and platform in a series fashion. This requires that each of the movable frames be moved to effect a movement of the platform. Thus, extra power will have to be expended to move all of the movable frames even though it may be desired to raise the platform to a height less than the height of one of said frames.
It is an object of this invention to provide an overhead service unit having a platform which will be vertically movable both with, and independently of, a series of vertically movable frames, and which will permit said platform to be movable from a fully lowered position in which a workman can easily step thereon to a fully raised position in which it is adjacent the upper end of the uppermost one of said vertically movable frames.